2 files changed, 19 insertions, 9 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index c1f9b3cf437c..5ad92419be19 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2217,14 +2217,8 @@ config RANDOMIZE_MEMORY_PHYSICAL_PADDING
            If unsure, leave at the default value.
 
 config HOTPLUG_CPU
-        bool "Support for hot-pluggable CPUs"
+        def_bool y
         depends on SMP
-        ---help---
-          Say Y here to allow turning CPUs off and on. CPUs can be
-          controlled through /sys/devices/system/cpu.
-          ( Note: power management support will enable this option
-            automatically on SMP systems. )
-          Say N if you want to disable CPU hotplug.
 
 config BOOTPARAM_HOTPLUG_CPU0
         bool "Set default setting of cpu0_hotpluggable"
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 025f419d16f6..6754f3ecfd94 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -564,6 +564,20 @@ static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
                 cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
 }
 
+static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
+{
+        if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
+                return true;
+        /*
+         * When CPU hotplug is disabled, then taking the CPU down is not
+         * possible because takedown_cpu() and the architecture and
+         * subsystem specific mechanisms are not available. So the CPU
+         * which would be completely unplugged again needs to stay around
+         * in the current state.
+         */
+        return st->state <= CPUHP_BRINGUP_CPU;
+}
+
 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                               enum cpuhp_state target)
 {
@@ -574,8 +588,10 @@ static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
                 st->state++;
                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
                 if (ret) {
-                        st->target = prev_state;
-                        undo_cpu_up(cpu, st);
+                        if (can_rollback_cpu(st)) {
+                                st->target = prev_state;
+                                undo_cpu_up(cpu, st);
+                        }
                         break;
                 }
         }